1. Field of the Invention
The present invention relates to novel cephem compounds and pharmaceutically acceptable salts thereof having potent antibacterial activities against gram-negative bacteria and an extended duration of action.
2. Description of the Prior Art
Since the first synthesis of cephem compounds in which the cephem nucleus has a carboxylic group at 4-position and a substituted amino group at 7-position, an extensive investigation has been made to develop a novel structure of cephem derivatives having more potent antibacterial activities and a broad antibacterial spectrum.
As prior art references which disclose such derivatives, U.S. Pat. No. 4,152,432 to Heymes et al.; U.S. Pat. No. 4,098,888 to Ochiai et al.; U.S. Pat. No. 4,258,041 to O'Callaghan; U.S. Pat. No. 4,748,172 to Katner; European Patent No. 0,318,552 to Katner; European Patent No. 0,164,944 to Bradbury; and European Patent No. 0,300,664 to Jung may be mentioned.
In most recent years, we have proposed, in our U.S. Ser. No. 07/896,667, now U.S. Pat. No. 5,281,589, a class of novel compounds having the formula: ##STR2##